I was told to stay away from Black thread. Black thread is usually made from the miscolored batches of thread and has had the opportunity to be redyed several times before they gave up on matching it. Every time it has been dyed it tends to loose its tensile strength and therefore it will break more often. Coats and Clarke are the worlds worse about participating in this practice.
I tested it for kicks and giggles with the set of gauges I use to set tensions up on sewing machines and every time the Black broke before the other colors. And I was using several different spools and brands to see if there was a difference. But the Coats and Clarke would break at half the amount of tension as their White.
Billy